1. Field of the Invention
The present invention relates generally to fields of motion picture, television and other multi-media production. More particularly, the invention relates to methods for synchronizing the media comprising a motion picture, television or other multi media production so as to facilitate viewing and editing.
2. Prior Art
Synchronization of multiple media sources is a problem which has plagued the motion picture production industry since the days of the early talkie movies. The techniques by which images are recorded on movie film and the techniques by which sound is recorded on a suitable sound recording medium naturally differ. Therefore, it has been common, since those early days, for two independent pieces of equipment to be used to record image and sound.
In the early days, images were invariably recorded as a sequence of frames on a continuous strip of photographic film. In contrast, sound was recorded as a microscopic wavy groove in either a wax cylinder or a wax disk. Some audio was recorded on the set, but much audio was recorded while observing a screening of the film.
Synchronization of a projected picture with corresponding audio was quite crude. Picture and audio would be started at a reference point established at the program. The speed of one or the other would be manually adjusted when loss of synchronization was observed. However, such techniques provide very poor synchronization, are unsuitable for synchronizing long programs and are unsuitable for synchronizing multiple tracks of audio with picture.
In modern studios, picture may be recorded on film or video tape, in a variety of formats. Audio is likely to be recorded on magnetic recording tape, also in a variety of formats. Whenever multiple tracks of source material are used to create a final production or composition, synchronization of one or more pictures with one or more tracks of audio may be required.
The use of a customary slate at the beginning of each take of a scene helps facilitate synchronization of audio recorded on the set with picture recorded on the set. The slate produces a sharp and distinct sound on the audio recording, simultaneous with an identifiable visual event, such as a bar hitting the top of the board. Additionally, during recording, the camera and the audio recording equipment may be mechanically or electrically synchronized, so that corresponding lengths of film and audio media are used. Consequently, to synchronize these source media for editing or viewing requires only that the sound of the slate in the audio track be aligned with the image of the bar hitting the top of the board. Then the two media may be mechanically or electrically locked together for playback or editing.
For greater flexibility, including the use of multiple tracks recorded either on the set or off the set, timecodes have been developed for aiding in the establishment and maintenance of synchronization in the circumstances such as described above. One type of commonly used timecode is that developed by the Society for Motion Picture and Television Engineers (SMPTE), which may be imprinted in an unused margin of the film or audio media during filming so as to indicate an absolute time reference for each frame of film. The imprinting of the SMPTE timecodes may be human readable, e.g., as numbers in the margin of the film, or may be machine readable, e.g. as bar codes in the margin of the film. Another time reference used on film media is the Eastman Kodak KEYKODE number. Among other things, the KEYKODE number acts as a roll and frame counter, by which any frame of a production may be absolutely identified. It is also recorded in the film margin, but KEYKODES are recorded on film stock at the time of manufacture.
Synchronization during playback may be achieved as follows. First, all the media are aligned manually to a starting point. During playback, timecodes are read off all of the media to be synchronized. The playback speeds of the media are then adjusted so as to cause the timecodes read off the media to coincide throughout the playback. Such systems employ standard feedback techniques to cause the playback speeds of all the media but one to follow the playback speed of the one.
However, the techniques discussed above are inadequate for modern electronic production and editing. As discussed above, current techniques still require physically aligning and synchronizing source media each time a source is to be played or edited. As noted above, this procedure requires manual alignment. It is therefore slow, labor-intensive and prone to error. Furthermore, at stages of production before a final editing sequence has been created, it is difficult to synchronize multi-track audio with cut film.
Systems are also available which can synchronously display digitized audio and video data. One such system is disclosed in Peters et al., U.S. Pat. No. 5,045,940. However, such systems assume synchronization between sources has previously been established. Another such system is commonly known as a lock box. A lock box performs crude synchronization between video and film. However, lock boxes do not accurately synchronize frame by frame, because they depend upon the frame rate of the source media, which differs between video and film.
Therefore, it is a general aim of the present invention to provide a method for synchronizing picture and audio in modern production and post production facilities. More generally stated, it is an aim of the present invention to provide a method of synchronizing a multi-media presentation at all stages of production and post-production.